1. Field
The present invention relates to a more efficient operation of plug-in electric vehicles.
2. Description of the Related Art
Conventional plug-in electric vehicles operate in a charge depletion mode until a minimum charge value has been reached and thereafter switches to a charge sustaining mode. However, such operations can be inefficient if the vehicle will travel a significant distance in charge sustaining mode. During such a trip, the state of charge (“SOC”) of an energy storage unit will be depleted during situations where it would be more efficient to use the energy conversion unit utilizing stored fuel to propel the vehicle and/or increase the SOC; or during the charge sustaining mode where the SOC is being maintained at some minimal level even when it is more efficient to increase or decrease the SOC via the energy conversion unit utilizing stored fuel.
Furthermore, conventional plug-in electric vehicles which have been operating for some time will inevitably operate in the charge sustaining mode maintaining a minimal SOC in the energy storage unit. However, the conventional plug-in electric vehicle may desire to enter a city, which is concerned about emissions. The city may prohibit the plug-in electric vehicle from utilizing its engine to provide direct motive power, generating electrical power to operate the motor, and/or charging the energy storage unit at all. Thus, the plug-in electric vehicle must operate in the charge depletion mode. Since conventional plug-in electrical vehicles only maintain a minimal SOC in the energy storage unit while in the charge sustaining mode, the plug-in electric vehicles will not be able to travel very far before they needs to be plugged in to be charged. Alternatively, conventional plug-in electric vehicles must avoid the city altogether. Neither outcomes are particularly desirable for a user who drives a plug-in electric vehicle and wants to travel through the city.
Thus, there is a need for a more efficient operation of automobiles, such as plug-in electric vehicles.